1. Field of the Invention
The present invention relates to an ultraviolet excitable aluminosilicate phosphor, and in particular relates to a white light illumination device utilizing the same.
2. Description of the Related Art
Commercially available white light illumination devices such as light emitting diodes (hereinafter LED), have gradually replaced conventional tungsten lamps or fluorescent lamps due to high luminescence efficiency and eco-friendliness. For white LEDs, the phosphor composition located within, is a critical factor determining luminescence efficiency, color rendering, color temperature, and lifespan of white LEDs.
In general, the excitation light source of conventional phosphors is a short wavelength ultraviolet light (UV) such as 147 nm, 172 nm, 185 nm, or 254 nm. The phosphors excited by the short wavelength UV have high light absorption and light transfer efficiency. Compared with phosphors excited by short wavelength UV, phosphors excited by long wavelength UV or visible light (250-470 nm) are rare.
In the field, conventional host materials in the phosphor are sulfides, nitrides, or oxides such as silicates or aluminates. Sulfides have high light transfer efficiency, but are unstable and easily degraded by moisture or oxygen. Meanwhile, nitrides are stable, but they are difficult to manufacture as nitrides require a high temperature/pressure condition, thus increasing costs and decreasing production yields. The properties of silicates and aluminates are suitable for white LEDs, however, wherein the preparation and application thereof are widely disclosed and discussed in several patents. Additionally, aluminosilicate phosphors are rarely utilized. Few aluminosilicate phosphors containing single activators are excited by vacuum UV or a cathode ray which can be applied in a plasma display or cathode ray tube. Most of the aluminosilicate phosphors, with co-dopant systems containing multi-activators, serve as afterglow phosphors (so-called light-storage materials). The application of aluminosilicate phosphors containing multi-activators excited by near UV (300-400 nm) has not been disclosed until now. Therefore, aluminosilicate phosphors excited by near UV to emit blue or blue-green light and collocate with other suitable phosphors to emit different colors to complete a white light illumination device are called for.